1. Field of the Invention
The invention relates to a technology of a rotary atomization coating apparatus that atomizes coating material into fine or coarse particles and deposits coating material particles onto a coating-object piece. More particularly, the invention relates to a technology for improving the cleaning characteristic of a rotary atomization coating apparatus in which coating material is sprayed into a rotating center cone and the atomized coating material is jetted.
2. Description of the Related Art
A known rotary atomization coating apparatus has, at a tip of a coating gun, an atomizer head that is rotated at high speed, and performs the coating by atomizing a coating material via the atomizer head and controlling the shape of coating material spraying by using shaping air or the like. The atomizer head atomizes coating material by causing a center cone provided in an inner part to spray coating material and spraying coating material by centrifugal force.
In the rotary atomization coating apparatus, the changing of coating colors involves the cleaning of the apparatus. To clean the rotary atomization coating apparatus, a thinner or the like is supplied as a cleaning agent to an inner part of the atomizer head via an ejection opening. In order to improve the cleaning characteristic of a known rotary atomization coating apparatus in which an cleaning thinner passage extending from a back side of an atomizer head inner part to a front side of the atomizer head inner part is provided in a central portion of the atomizer head inner part, the thinner passage is designed so that a portion of the thinner passage portion located at a side of outlet to the front side of the atomizer head inner part has a shape that becomes progressively larger toward the front side of the atomizer head inner part (e.g., see Patent Literature 1).                [Patent Literature 1]        Japanese Patent Application Laid-Open Publication No. 8-215611        
However, in the rotary atomization coating apparatus in which a cleaning thinner passage portion becomes progressively larger toward the front side of the atomizer head inner part, sprayed coating material may sometimes bounce inside the atomizer head inner part to deposit on an inner surface of the atomizer head inner part.
If inside the atomizer head inner part, coating material is sprayed to the back side of a forward portion of the atomizer head inner part, the coating material bounces from the back side of the forward portion of the atomizer head inner part and then deposits on the front side of a rearward portion of the atomizer head inner part.